Re: [RFC PATCH net] ethtool: Fix incompatibility between netlink and ioctl interfaces

On Wed, Sep 30, 2020 at 11:06:53PM +0300, Ido Schimmel wrote:

On Wed, Sep 30, 2020 at 10:59:17AM +0200, Michal Kubecek wrote:

quoted

How about this compromise? Let's introduce a "legacy" flag which would
allow "ethtool -s <dev> autoneg on" do what it used to do while we would
not taint the kernel-userspace API with this special case so that
ETHTOOL_MSG_LINKMODES_SET request with only ETHTOOL_A_LINKMODES_AUTONEG
(but no other attributes like _SPEED or _DUPLEX) would leave advertised
link modes untouched unless the "legacy" flag is set. If the "legacy"
flag is set in the request, such request would set advertised modes to
all supported.

Sorry for the delay, busy with other obligations. Regarding the "legacy"
flag suggestion, do you mean that the ethtool user space utility will
always set it in ETHTOOL_MSG_LINKMODES_SET request in order to maintain
backward compatibility with the ioctl interface?

Yes, that is what I meant. We could also do the opposite (ioctl
compatibility by default and a flag for the way it works now) but
I would prefer the default (on userspace-kernel API level) to be "only
ETHTOOL_A_LINKMODES_AUTONEG attribute means we only want to switch
autonegotiation and touch nothing else".

Michal